Baseline variables: To be sure the groups are comparable and that known risk factors are equally distributed among both groups, we will record the following: demographic variables (sex, gestational age, birth weight, weight at surgery, age at surgery, mother's years of schooling, father's socioeconomic status); preoperative variables (cardiac diagnosis, cyanosis preoperatively (oxygen saturation <85%), single/biventricular heart physiology, days on mechanical ventilation, inotrope score, lowest Pa02, highest lactate, and highest base deficit); and intraoperative variables (lactate level and troponin I level before CPB, duration of inhalational anesthetic, CPB time, aortic cross clamp time, DHCA use, DHCA duration, and re-CPB in the operating room).